Manufacturing method of organic thin film transistor

ABSTRACT

A method for manufacturing an organic thin film transistor includes steps of: forming a graphene layer on a surface of a metal substrate; covering a surface of the graphene layer with an organic solution and heating the graphene layer to form organic semiconductor nano lines on the surface of the graphene layer; and transferring the organic semiconductor nano lines to a target substrate. The graphene layer is formed on the surface of the metal substrate in mass production. The organic semiconductor nano lines (monocrystalline semiconductor) are grown in mass production by the graphene layer. The semiconductor layer having organic thin film transistors is formed after transferring the organic semiconductor nano lines on the target substrate. A large amount of the organic semiconductor nano lines can be formed simultaneously on the surface of the metal substrate with a large area.

CROSS REFERENCE

This is a divisional application of co-pending U.S. patent applicationSer. No. 14/544,015, filed on Jul. 16, 2017, which is a national stageof foreign priority of PCT Application No. PCT/CN2017/082630, filed onApr. 28, 2017, claiming foreign priority of Chinese Patent ApplicationNo. 201710245003.5, entitled “Manufacturing method of organic thin filmtransistor”, filed on Apr. 14, 2017, the disclosure of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present application relates to a display technology field, and moreparticularly to a manufacturing method of an organic thin filmtransistor.

BACKGROUND OF THE INVENTION

With the continuous progress of display technology, the flexible displaydevice gradually appears in the market and the novel appearance of theflexible display device has a great attraction to the user. The ThinFilm Transistors (TFT) are located on the array substrate of theflexible display device and are important elements of controlling thework of the Organic Light Emitting Diodes (OLED). The Organic Thin FilmTransistors (OTFT) are thin film transistors made of organic material.In comparison with the flexible OLED display device based on LowTemperature Poly-silicon (LTPS) TFT or Indium Gallium Zinc Oxide (IGZO)TFT, the flexible OLED display device based on OTFT utilizes organicmaterial, of which the flexibility is much higher than that of inorganicmaterial (silicon semiconductor or metal oxide semiconductor). Nofracture after many times of bending appears to significantly promotethe ability of the flexible display device to withstand bending.Accordingly, the OTFT with the good bending property can replace theinorganic TFT in the flexible display field.

In prior art, the fabrication of OTFT utilizes vacuum deposition orsolution treatment. The consumed time of manufacture process is longerand the production scale is small. The fabrication of OTFT is limited bythe production process and equipment, resulting in the inability tocarry out large-scale production to lead to the low production capacityof the display devices and the increase in the production cost.

SUMMARY OF THE INVENTION

On this account, the technical issue to be solved by the presentapplication is to provide a manufacturing method of an organic thin filmtransistor to solve the issue that the fabrication of OTFT in prior artis limited by the production process and equipment, resulting in theinability to carry out large-scale production to lead to the lowproduction capacity of the display devices and the increase in theproduction cost.

The manufacturing method of the organic thin film transistor comprisessteps of:

forming a graphene layer on a surface of a metal substrate;

covering a surface of the graphene layer with organic solution andheating the graphene layer to form an organic semiconductor nano line onthe surface of the graphene layer; and

transferring the organic semiconductor nano line on a target substrate.

A plurality of organic semiconductor nano lines form an organicsemiconductor nano line set in a transfer printing manner astransferring the organic semiconductor nano line.

The transfer printing manner is a roll-to-roll transfer printing or aroll-to-sheet transfer printing.

The step of forming the graphene layer on the surface of the metalsubstrate comprises: depositing methane gas and hydrogen by chemicalvapor deposition on the surface of the metal substrate at an ambienttemperature of not lower than 1000 Celsius degrees, wherein the metalsubstrate is a copper substrate.

A plurality of organic semiconductor nano lines form an organicsemiconductor nano line set in a transfer printing manner astransferring the organic semiconductor nano line.

The transfer printing manner is a roll-to-roll transfer printing or aroll-to-sheet transfer printing.

The organic solution is a mixed solution of9,10-bis-phenylethynylanthracene and dimethylformamide.

A plurality of organic semiconductor nano lines form an organicsemiconductor nano line set in a transfer printing manner astransferring the organic semiconductor nano line.

The transfer printing manner is a roll-to-roll transfer printing or aroll-to-sheet transfer printing.

A concentration of 9,10-bis-phenylethynylanthracene in the organicsolution is 0.004 mol/liter to 0.012 mol/liter.

A plurality of organic semiconductor nano lines form an organicsemiconductor nano line set in a transfer printing manner astransferring the organic semiconductor nano line.

The transfer printing manner is a roll-to-roll transfer printing or aroll-to-sheet transfer printing.

A temperature of heating the graphene layer is not higher than 50Celsius degrees and a heating time is not less than 48 hours.

A plurality of organic semiconductor nano lines form an organicsemiconductor nano line set in a transfer printing manner astransferring the organic semiconductor nano line.

The transfer printing manner is a roll-to-roll transfer printing or aroll-to-sheet transfer printing.

The target substrate comprises a gate electrode, a gate insulationlayer, a source and a drain, which are sequentially formed and stacked.

After the step of transferring the organic semiconductor nano line onthe target substrate, the method further comprises a step of etching theorganic semiconductor nano line to form a semiconductor channel.

The target substrate comprises a gate electrode and a gate insulationlayer, which are sequentially stacked; and after the step oftransferring the organic semiconductor nano line on the targetsubstrate, the method further comprises a step of forming a source and adrain on a side of the organic semiconductor nano line away from thegate insulation layer.

After the step of transferring the organic semiconductor nano line onthe target substrate, the method further comprises a step of etching theorganic semiconductor nano line to form a semiconductor channel.

The benefits of the present application are: the graphene layer isformed on the surface of the metal substrate in mass production. Theorganic semiconductor nano lines (monocrystalline semiconductor) aregrown in mass production by graphene layer. The semiconductor layerhaving organic thin film transistors are formed after transferring theorganic semiconductor nano lines on the target substrate. A large amountof the organic semiconductor nano lines can be formed at a time on thesurface of the metal substrate with a large area. The transferringskills of roll-to-roll and roll-to-sheet are mutual and can transfer theorganic semiconductor nano lines of the metal substrate on the targetsubstrate in mass production rapidly and with high quality for reducingthe consumed time of manufacture process and satisfying the requirementof mass production. The production capacity of display device is highand the production cost is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly explain the technical solution in theembodiments of the present invention, the following figures will bedescribed in the embodiments are briefly introduced. It is obvious thatthe drawings are merely some embodiments of the present application,those of ordinary skill in this field can obtain other figures accordingto these figures without paying the premise.

FIG. 1 is a flowchart of a manufacturing method of an organic thin filmtransistor provided by the embodiment of the present application.

FIG. 2 is diagram of step S102 in a manufacturing method of an organicthin film transistor provided by the embodiment of the presentapplication.

FIG. 3 is diagram of step S103 in a manufacturing method of an organicthin film transistor provided by the embodiment of the presentapplication.

FIG. 4 is a top view diagram of a target substrate provided by theembodiment of the present application.

FIG. 5 and FIG. 6 are structure diagrams of the organic thin filmtransistor made by the manufacturing method of the organic thin filmtransistor provided by the embodiment of the present application.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present application are described in detail with thetechnical matters, structural features, achieved objects, and effectswith reference to the accompanying drawings as follows. It is clear thatthe described embodiments are part of embodiments of the presentapplication, but not all embodiments. Based on the embodiments of thepresent application, all other embodiments to those of ordinary skill inthe premise of no creative efforts obtained, should all be consideredwithin the scope of protection of the present application.

FIG. 1 is a flowchart of a manufacturing method of an organic thin filmtransistor provided by the embodiment of the present application. Asshow in figure, the manufacturing method of the organic thin filmtransistor provided by the embodiment of the present applicationcomprises steps of:

S101, forming a graphene layer 12 on a surface of a metal substrate 10.

In the present embodiment, the graphene layer 12 is formed on thesurface of the metal substrate 10 by chemical vapor deposition. TheChemical Vapor Deposition (CVD) is a method of vapor deposition ofmaterial preparation, which introduces one or more compounds andmonolithic gases constructing a thin film element into a reactionchamber, in which a substrate is placed and a solid film is deposited onthe surface of the substrate by means of space gas chemical reaction. Inthis embodiment, the chemical vapor deposition is used. Two reactiongases are introduced into the reaction chamber to form the graphenelayer 12 (graphene thin film) on the metal substrate 10 in the reactionchamber. Graphene is a honeycomb planar film formed by sp2 hybridizationof carbon atoms, which is a quasi-two-dimensional material with only oneatomic layer thickness, so also named monatomic layer graphene.Specifically, the metal substrate 10 is a substrate made of coppermaterial. The chemical properties of the copper substrate are relativelystable. The copper substrate is not easy to react chemically with thereaction gas. The thermal conductivity of the copper substrate is goodand the homogeneous graphene film can be formed in the high temperaturereaction chamber. Furthermore, the gases used are methane gas (CH4) andhydrogen (H2) and the reaction chamber is set at a temperature of notlower than 1000 Celsius degrees. In one preferred embodiment, thereaction result is the best when the environment temperature in thereaction chamber is 1035 Celsius degrees. In this embodiment, the volumeratio of methane gas to hydrogen introduced into the reaction chamber is2:1. Then, the effect of forming the graphene thin film on the coppersubstrate is the best.

Since the graphene layer 12 is formed on the surface of the metalsubstrate 10, the area of the graphene layer 12 depends on the size ofthe metal substrate 10 and the amount of the reaction gas introducedinto the reaction chamber. Theoretically the area of the graphene layer12 can be increased by increasing the size of the metal substrate 10 andincreasing the amount of the reaction gas. The graphene layer 12 with alarge area can provide a large amount of organic semiconductor nanolines 14 for the mass production of organic thin film transistors. Therequirements of large-scale production can be met to improve productionefficiency, to save production capacity and to reduce production cost.

S102, covering a surface of the graphene layer 12 with organic solutionand heating the graphene layer 12 to form an organic semiconductor nanoline 14 on the surface of the graphene layer 12.

Please refer to FIG. 2. After the organic solution is uniformly droppedand coated on the surface of the graphene layer 12, the metal substrate10 with the graphene layer 12 is placed in an oven and heated for awhile and the solvent is evaporated. The organic semiconductor nano line14, which is perpendicular with the metal substrate 10 is formed on thesurface of the graphene layer 12. Furthermore, an amount of the organicsemiconductor nano lines 14 is plural and the organic semiconductor nanolines are distributed on the surface of the graphene layer 12.

In this embodiment, the organic solution is a mixed solution of9,10-bis-phenylethynylanthracene (BPEA) and dimethylformamide (DMF). Themolecular formula of 9,10-bis-phenylethynylanthracene is C30H18 and themolecular formula of dimethylformamide is C3H7NO. Furthermore, in theorganic solution, a concentration of the9,10-bis-phenylethynylanthracene determines the length of the organicsemiconductor nano line 14 grown on the metal substrate 10.Specifically, the concentration of the 9,10-bis-phenylethynylanthraceneis 0.004 mol/L to 0.012 mol/L. The length a of the organic semiconductornano line 14 obtained is 7 μm to 15 μm. The organic semiconductor nanolines 14 of various lengths can be obtained by adjusting theconcentration of the 9,10-bis-phenylethynylanthracene in the organicsolution. The organic thin film transistors of various specificationscan be manufactured for satisfying the design demands of differentdisplay devices.

In this embodiment, a temperature of heating the graphene layer 12 isnot higher than 50 Celsius degrees and a heating time is not less than48 hours. Specifically, the heating temperature is set at 50 Celsiusdegrees and the heating time is set to 48 hours. The organic solutioncan be sufficiently evaporated to form a sufficient amount of theorganic semiconductor nano line 14.

The metal substrate 10 of large size provides the graphene layer 12 withthe large area. A large amount of organic semiconductor nano lines 14can be formed with the graphene layer 12 with the large area for themass production of organic thin film transistors to achieve the massproduction. Specifically, the graphene layer 12 uses the metal substrate10 to be the base and is formed on the surface of the metal substrate10. Then, with increasing the size of the metal substrate 10, the areaof the graphene layer 12 formed on the surface of the metal substrate 10with one time chemical vapor deposition is larger. Thus, the amount ofthe organic semiconductor nano lines 14 formed on the graphene layer 12is more. Namely, with increasing size of the metal substrate 10, thelarge amount of the organic semiconductor nano lines 14 can be formedwith one step S101 and one step S102. After the organic semiconductornano line 14 is transferred on a target substrate in a transfer printingmanner and the organic thin film transistor is formed on the surface ofthe target substrate, the display panel with target size is obtainedafter cutting. More display panels can be obtained after cutting byincreasing the size of the target substrate. More organic semiconductornano lines 14 are required for the size increase of the targetsubstrate. The metal substrate 10 of large size is correspondinglyneeded as transfer printing. Accordingly, more organic semiconductornano lines 14 can be provided for the target substrate by increasing thesize of the metal substrate 10. More display panels can be formed on onetarget substrate at the same time to production efficiency and aresuitable for mass production.

S103, transferring the organic semiconductor nano line 14 on a targetsubstrate 20.

Please refer to FIG. 3 at the same time. In this embodiment, the organicsemiconductor nano line 14 is transferred on the target substrate 20 ina transfer printing matter. The target substrate 20 is a display panelof composing a display panel. The transfer printing matter is aroll-to-roll transfer printing or a roll-to-sheet transfer printing. Theroll-to-roll process is a high-performance, low-cost continuousproduction method. The object to be treated is a thin film with aflexible property. The material of the flexible board is plastic or astainless steel sheet with a thickness less than 0.1 mm. After theflexible board is unwound from a cylindrical roll, a specific purposefunction is added to the flexible board or the surface of the flexibleboard is processed. Then, the flexible board is rewound in acylindrical, again or is directly cut to be an end product. The specificprocesses comprises Unwind, Process, Rewind and Cutting. The combinationof the roll-to-roll processes on the surface of the flexible boardcomprises several major processes, such as Embossing, Laminate, Coatingand Printing. In this embodiment, the target substrate 20 is theflexible board. The target substrate 20 is a main support element of aflexible display and elements such as a thin film transistor and anorganic light emitter are configured on the target substrate 20. Thetarget substrate 20 is processed after being unwound. The process is totransfer the organic semiconductor nano line 14 on the surface of themetal substrate 10 on the target substrate 20 in a press printing manneror a laminate manner. Specifically, the organic semiconductor nano line14 faces the target substrate 20 and the metal substrate 10 is kept tobe inclined to the target substrate 20. One end of the organicsemiconductor nano line 14 away from the graphene layer 12 firstcontacts with the target substrate 20 and then the organic semiconductornano line 14 is attached on the target substrate 20 from one end awayfrom the graphene layer 12 to one end connected to the graphene layer 12in the length direction. In this step, the large amount of the organicsemiconductor nano line 14 perpendicular with the metal substrate 10 arerapidly tilted and transferred on the target substrate 20 to form thesemiconductor layer 142 having organic thin film transistors forsatisfying the requirement of mass production of organic thin filmtransistors.

With combination of FIG. 4, the length direction of the organicsemiconductor nano line 14 transferred on the target substrate 20 isparallel with the surface of the target substrate 20. Furthermore, aplurality of organic semiconductor nano lines 14 are transferred at thesame time to form an organic semiconductor nano line set 140 astransferring the organic semiconductor nano line 14. Each organicsemiconductor nano line set 140 corresponds to one pair of source 502and drain 504. In this embodiment, each organic semiconductor nano lineset 140 comprises four organic semiconductor nano lines 14, which arearranged in parallel. A plurality of organic semiconductor nano linesets 140 are arranged in array. Each organic semiconductor nano line set140 corresponds to one pair of source 502 and drain 504. Namely, eachorganic semiconductor nano line set 140 correspondingly forms an organicthin film transistor. By changing the amount of the organicsemiconductor nano lines 14 of each organic semiconductor nano line sets140, various organic semiconductor layers 142 can be formed on thetarget substrate 20. The organic thin film transistors of variousspecifications can be manufactured to meet production need and toimprove production efficiency.

In one embodiment, before the organic semiconductor nano line 14 istransferred on the target substrate 20, a gate electrode 30, a gateinsulation layer 40, a source electrode 502 and a drain 504, which aresequentially formed and stacked on the target substrate 20.Specifically, the gate electrode 30 is made of a conductive material.The gate insulation layer 40 is an insulation material to insulate thegate electrode 30 and the organic semiconductor layer 142. In onepreferred embodiment, the gate insulation layer 40 is made of an organicmaterial to promote the flexibility of the flexible display device.After the organic semiconductor layer 142 is formed on the targetsubstrate 20, the manufactured structure of the organic thin filmtransistor is shown in FIG. 5. Furthermore, the organic thin filmtransistor formed in this embodiment is a button contact OTFT. Themanufacture process of the button contact OTFT is simple and canpartially protect the source 502 and the drain 504.

In another embodiment, before the organic semiconductor nano line 14 istransferred on the target substrate 20, a gate electrode 30 and a gateinsulation layer 40 are sequentially formed and stacked on the targetsubstrate 20. After the organic semiconductor nano line 14 istransferred on the target substrate 20, a source 502 and a drain 504 areformed on a side of the organic semiconductor nano line 14 away from thegate insulation layer 40. Specifically, the gate electrode 30 is made ofa conductive material. The gate insulation layer 40 is an insulationmaterial to insulate the gate electrode 30 and the organic semiconductorlayer 142. In one preferred embodiment, the gate insulation layer 40 ismade of an organic material to promote the flexibility of the flexibledisplay device. After the organic semiconductor layer 142 is formed onthe target substrate 20, the manufactured structure of the organic thinfilm transistor is shown in FIG. 6. Furthermore, the organic thin filmtransistor formed in this embodiment is a top contact OTFT. Themanufacture process of the top contact OTFT is simple.

In this embodiment, after the organic semiconductor nano line 14 istransferred on the target substrate 20 to form the organic semiconductorlayer 142, the organic semiconductor nano line 14 (organic semiconductorlayer 142) on the target substrate 20 is etched to form a semiconductorchannel. The channel is a conductive layer that is caused by an appliedelectric field in the length direction in the semiconductor forconnecting the source 502 and the drain 504. Furthermore, the designedchannel direction is along the length direction of the organicsemiconductor nano line 14 to connect the source 502 and the drain 504at two ends of the organic semiconductor nano line 14.

The graphene layer 12 is formed on the surface of the metal substrate 10in mass production. The organic semiconductor nano lines 14(monocrystalline semiconductor) are grown in mass production by graphenelayer 12. The semiconductor layer 142 having organic thin filmtransistors are formed after transferring the organic semiconductor nanolines 14 on the target substrate 20. A large amount of the organicsemiconductor nano lines 14 can be formed at a time on the surface ofthe metal substrate 10 with a large area. The transferring skills ofroll-to-roll and roll-to-sheet are mutual and can transfer the organicsemiconductor nano lines 14 of the metal substrate 10 on the targetsubstrate 20 in mass production rapidly and with high quality forreducing the consumed time of manufacture process and satisfying therequirement of mass production. The production capacity of displaydevice is high and the production cost is reduced.

The foregoing descriptions are merely the specific embodiments of thepresent application. However, the present application is not limitedthereby. Any modifications, equivalent replacements or improvementswithin the spirit and principles of the embodiment described above,which can be easily derived by those skilled persons in this art fromthe technical field disclosed in the present application should becovered by the protected scope of the application. Thus, the patentprotection scope of the present application should be subjected to whatis claimed is.

What is claimed is:
 1. A manufacturing method of an organic thin filmtransistor, comprising steps of: forming a graphene layer on a surfaceof a metal substrate; covering a surface of the graphene layer with anorganic solution and heating the graphene layer to form organicsemiconductor nano lines on the surface of the graphene layer; andtransferring the organic semiconductor nano lines to a target substrate;wherein the step of forming a graphene layer on a surface of a metalsubstrate comprises: depositing methane gas and hydrogen by chemicalvapor deposition on the surface of the metal substrate at an ambienttemperature of not lower than 1000 Celsius degrees, wherein the metalsubstrate is a copper substrate; wherein a plurality of organicsemiconductor nano lines form an organic semiconductor nano line set ina transfer printing manner as transferring the organic semiconductornano lines; and wherein the target substrate comprises a gate electrodeand a gate insulation layer, which are sequentially stacked; and afterthe step of transferring the organic semiconductor nano lines to thetarget substrate, the method further comprises a step of forming asource and a drain on a side of the organic semiconductor nano line awayfrom the gate insulation layer.
 2. The manufacturing method of theorganic thin film transistor according to claim 1, wherein the transferprinting manner is a roll-to-roll transfer printing or a roll-to-sheettransfer printing.
 3. The manufacturing method of the organic thin filmtransistor according to claim 1, wherein the organic solution is a mixedsolution of 9,10-bis-phenylethynylanthracene and dimethylformamide. 4.The manufacturing method of the organic thin film transistor accordingto claim 1, wherein a temperature of heating the graphene layer is nothigher than 50 Celsius degrees and a heating time is not less than 48hours.
 5. The manufacturing method of the organic thin film transistoraccording to claim 1, wherein after the step of transferring the organicsemiconductor nano lines to the target substrate, the method furthercomprises a step of etching the organic semiconductor nano lines to forma semiconductor channel.